import pandas as pd
import numpy as np

df = pd.DataFrame({'A': [1, 2, 3, 4, 5], 'B': [1, 4, 2, 6, 5]})

# get the positions where values of columns A and B match
mask = np.where(df['A'] == df['B'])[0]
matches = df.index[mask]
print(matches)